Most often in May, 24 days.
Highest follower count seen that year: 179,931.
January
Jan 1 18:00–20:00 Jan 3 16:00–18:00 Jan 5 19:00–21:00 Jan 6 15:00–17:00 Jan 7 17:00–21:00 Jan 8 17:00–19:00 Jan 9 19:00–21:00 Jan 10 22:00–23:00 Jan 11 20:00–24:00 Jan 13 23:00–24:00 Jan 14 00:00–01:00 Jan 15 21:00–22:00 Jan 16 00:00–01:00 Jan 17 21:00–23:00 Jan 18 16:00–18:00 Jan 19 23:00–24:00 Jan 21 22:00–23:00 Jan 22 23:00–24:00 Jan 23 21:00–22:00 Jan 24 23:00–24:00 Jan 25 00:00–01:00 Jan 26 20:00–22:00 Jan 29 00:00–03:00 Jan 31 19:00–24:00
February
Feb 3 00:00–06:00 Feb 4 02:00–06:00, 08:00–12:00 Feb 5 14:00–20:00 Feb 7 05:00–09:00 Feb 9 17:00–19:00 Feb 11 16:00–18:00 Feb 13 16:00–18:00 Feb 14 17:00–19:00 Feb 16 16:00–20:00 Feb 18 19:00–21:00 Feb 19 16:00–19:00 Feb 20 19:00–21:00 Feb 22 23:00–24:00 Feb 23 00:00–01:00, 22:00–24:00 Feb 24 17:00–19:00 Feb 25 20:00–21:00 Feb 27 17:00–18:00 Feb 28 23:00–24:00
March
Mar 1 00:00–01:00, 22:00–24:00 Mar 2 21:00–22:00 Mar 4 20:00–24:00 Mar 6 02:00–04:00, 20:00–22:00 Mar 7 23:00–24:00 Mar 8 00:00–03:00 Mar 10 02:00–03:00 Mar 11 02:00–07:00 Mar 13 11:00–13:00 Mar 14 18:00–21:00 Mar 15 12:00–13:00 Mar 17 19:00–23:00 Mar 19 15:00–17:00 Mar 20 08:00–10:00, 17:00–18:00 Mar 21 20:00–21:00 Mar 22 10:00–12:00, 18:00–22:00 Mar 23 16:00–18:00 Mar 24 21:00–22:00 Mar 27 19:00–20:00 Mar 28 15:00–17:00 Mar 29 19:00–22:00 Mar 30 15:00–17:00 Mar 31 22:00–24:00
April
Apr 1 21:00–22:00 Apr 2 20:00–21:00 Apr 3 21:00–23:00 Apr 5 02:00–04:00, 20:00–22:00 Apr 10 13:00–14:00 Apr 21 17:00–18:00 Apr 22 15:00–18:00 Apr 24 15:00–20:00 Apr 25 16:00–20:00 Apr 27 13:00–15:00 Apr 29 10:00–13:00, 17:00–19:00
May
May 1 16:00–20:00 May 2 14:00–16:00, 20:00–22:00 May 3 17:00–20:00 May 4 22:00–24:00 May 6 17:00–20:00, 23:00–24:00 May 7 21:00–24:00 May 8 00:00–01:00 May 9 02:00–03:00 May 10 03:00–05:00 May 11 02:00–05:00, 07:00–08:00 May 13 09:00–16:00 May 14 13:00–15:00 May 15 16:00–18:00 May 19 13:00–16:00 May 20 15:00–20:00 May 21 14:00–17:00 May 23 09:00–12:00 May 24 15:00–20:00 May 25 15:00–19:00 May 26 20:00–22:00 May 27 14:00–18:00 May 28 21:00–24:00 May 30 18:00–21:00 May 31 19:00–22:00
June
Jun 4 16:00–19:00, 23:00–24:00 Jun 5 00:00–01:00 Jun 6 23:00–24:00 Jun 7 00:00–03:00 Jun 8 01:00–03:00, 06:00–09:00 Jun 10 09:00–10:00 Jun 11 04:00–06:00 Jun 15 20:00–21:00 Jun 16 08:00–09:00, 13:00–16:00 Jun 17 18:00–20:00 Jun 18 19:00–21:00 Jun 21 21:00–22:00 Jun 23 21:00–22:00 Jun 24 17:00–19:00 Jun 25 20:00–22:00 Jun 26 18:00–20:00 Jun 28 18:00–19:00 Jun 29 19:00–20:00 Jun 30 01:00–02:00
July
Jul 1 11:00–12:00 Jul 5 00:00–03:00 Jul 6 09:00–12:00 Jul 9 13:00–15:00 Jul 10 13:00–15:00 Jul 11 03:00–05:00 Jul 12 04:00–05:00, 08:00–09:00, 11:00–13:00 Jul 14 04:00–05:00 Jul 16 15:00–17:00 Jul 17 17:00–18:00 Jul 18 20:00–21:00 Jul 22 17:00–19:00 Jul 23 20:00–22:00
August
Aug 7 17:00–20:00 Aug 8 17:00–20:00 Aug 10 20:00–22:00 Aug 11 20:00–22:00 Aug 12 23:00–24:00 Aug 13 00:00–01:00 Aug 14 23:00–24:00 Aug 18 02:00–06:00 Aug 19 01:00–03:00 Aug 20 14:00–16:00 Aug 23 16:00–18:00 Aug 24 18:00–20:00 Aug 26 16:00–18:00 Aug 27 21:00–22:00
September
Sep 12 17:00–19:00 Sep 14 18:00–20:00 Sep 15 18:00–20:00 Sep 16 18:00–19:00 Sep 17 20:00–22:00 Sep 18 23:00–24:00 Sep 20 23:00–24:00 Sep 25 07:00–08:00 Sep 26 21:00–22:00 Sep 28 22:00–24:00 Sep 29 00:00–01:00 Sep 30 02:00–04:00, 09:00–10:00
October
Oct 2 02:00–05:00 Oct 3 17:00–19:00 Oct 5 16:00–20:00 Oct 6 08:00–11:00, 15:00–17:00 Oct 9 10:00–12:00, 16:00–19:00 Oct 10 19:00–20:00 Oct 11 17:00–20:00 Oct 13 21:00–22:00 Oct 15 20:00–21:00 Oct 16 17:00–20:00 Oct 17 22:00–23:00 Oct 18 20:00–22:00 Oct 19 19:00–21:00 Oct 20 19:00–20:00 Oct 21 21:00–24:00 Oct 22 23:00–24:00 Oct 23 00:00–01:00 Oct 26 00:00–01:00, 21:00–22:00 Oct 30 01:00–06:00
November
Nov 2 04:00–07:00 Nov 4 13:00–15:00 Nov 6 17:00–20:00 Nov 7 20:00–21:00 Nov 10 18:00–22:00 Nov 12 18:00–20:00 Nov 14 18:00–21:00 Nov 15 16:00–18:00, 20:00–21:00 Nov 16 16:00–19:00 Nov 17 20:00–23:00 Nov 19 20:00–22:00 Nov 20 18:00–21:00 Nov 21 21:00–24:00 Nov 22 05:00–07:00 Nov 24 00:00–02:00 Nov 25 00:00–02:00 Nov 27 04:00–06:00 Nov 30 08:00–09:00
December
Dec 1 11:00–13:00, 16:00–19:00 Dec 3 13:00–20:00 Dec 4 19:00–20:00 Dec 5 18:00–19:00 Dec 11 16:00–19:00 Dec 12 18:00–23:00 Dec 13 19:00–21:00 Dec 14 20:00–23:00 Dec 16 17:00–19:00 Dec 17 22:00–24:00 Dec 18 00:00–01:00 Dec 19 23:00–24:00 Dec 20 00:00–02:00 Dec 21 23:00–24:00 Dec 22 00:00–02:00 Dec 23 00:00–02:00 Dec 25 00:00–03:00 Dec 27 03:00–06:00